In, for example, digital radio designs there are a large number of signal paths containing high-speed, high-resolution digital data. Typical examples are: (a) from an ADC (Analog-to-Digital Converter) to a subsequent DSP (Digital Signal Processor); (b) from a DSP to a DAC (Digital-to-Analog Converter) used in a radio transmitter; (c) between DSPs within a radio base station; (d) between sub-systems within a radio base station, e.g. between different boards.
It is desirable to reduce the amount of routing between ASICs (Application Specific Integrated Circuits), FPGAs (Field-Programmable Gate Arrays), ADCs and DACs. In order to do that, DSPs and data-converter parts are migrating towards the use of bit-serial, rather than bit-parallel digital interfaces. Some benefits are:                The digital interface between ADCs/DACs and ASICs results in a substantially reduced number of bus wires, thus reducing the board space occupied by signal routing.        Dramatically reduced number of output/input pins per component allows for integration of more functionality in a single package, thus further reducing board space. An example is dual/quad/octal ADCs/DACs. It also theoretically enables a larger number of digital signal paths to be handled by a single ASIC before becoming constrained by the pin-count.        A bit-serial interface may use any available electrical standards, such as LVDS (Low-Voltage Differential Signaling) and CML (Current-Mode Logic), or a custom technology. Available coding standards, such as 8 b/10 b-coding may or may not be used, and the clock may or may not be embedded in the data bit-stream (for very high bit-rates, e.g. over 1 Gb/s, an embedded clock/sync is usually preferred over an extra clock line in parallel with the data).        
A bit-serial channel with embedded clock/sync has the disadvantage that frame marker bits or bit patterns have to be inserted into the transmission to mark the start and/or stop of a transmission frame. The repetitive nature of such start/stop markers generates spurious spectral lines at k*fb/n, where fb is the bit-rate of the bit-serial channel, n is the transmission frame length in bits, and k is an integer. The end result is that these spurious spectral lines may lead to undesirable interference.